SAN JUAN, Puerto Rico -- Rick Santorum holds up his latest two upsets as evidence that GOP front-runner Mitt Romney is "fundamentally flawed." But Romney said Wednesday he's won a million more votes than Santorum in the presidential nominating contest and that should prove his widespread appeal.

Romney, who's scooped up more delegates than his three rivals combined, rejected suggestions that occasional gaffes highlighting his multimillion-dollar personal wealth leave him unable to connect to regular voters.

"I made a lot of money. I've been very successful. I'm not going to apologize for that," Romney said in a Fox News interview, his first appearance since finishing third in Alabama and Mississippi on Tuesday.

Romney said a string of wins in states as diverse as Florida, Ohio, New Hampshire and Hawaii show he can appeal to independents, tea partyers, women and voters across income groups.

"You don't win a million more votes than anyone else in this race by just appealing to high-income Americans," he said.

As the contest moved on to Puerto Rico, Illinois, Louisiana and beyond, Romney stopped for two days of fundraising in New York. Santorum headed straight to San Juan to keep testing Romney's lead.

"If we keep winning races, eventually people are going to figure out that Gov. Romney is not going to be the nominee," he told reporters gathered Wednesday outside the governor's mansion.

Santorum's wins in the Alabama and Mississippi primaries Tuesday night effectively shut the door on Newt Gingrich's strategy of resuscitating his campaign in the South, where he hoped to establish himself as regional favorite son.

Santorum would not say it was time for Gingrich to quit the race. But his campaign advisers have made plain their wish that the former U.S. House speaker from Georgia step aside and stop drawing the same conservative votes Santorum needs.

Santorum and Gingrich accounted for an overwhelming majority of votes in the two Southern primaries Tuesday, while Romney held his ground in the delegate chase by winning caucuses in Hawaii and American Samoa.

Santorum said the former Massachusetts governor should be winning easily, given his overwhelming financial advantage.

"There's something fundamentally right with what we're doing and the message we're delivering and there's something fundamentally flawed about the person we're running against," he said of Romney.

Gingrich also has been criticizing Romney, labeling him a weak front-runner. Romney shot back with what sounded like a schoolyard taunt Wednesday: "If I'm a weak front-runner, what does that make Newt Gingrich?"

The race now turns to caucuses Saturday in Missouri, where Santorum and Romney already have invested substantial time, and Puerto Rico's primary on Sunday, which is drawing rare attention in a year when the race has drawn out longer than most.

Romney wasn't slated to arrive in the U.S. territory until Friday, after spending two days in New York City raising money.

Romney already is spending to dominate the airwaves in Illinois, which will offer a hefty 54 delegates in voting Tuesday. His campaign has put down almost $1 million for Illinois TV advertising, on top of $2.4 million spent there by a supportive super PAC.

Romney's seemingly unassailable delegate lead left his opponents' campaigns talking about less orthodox ways to stop him. John Brabender, senior strategist for the Santorum campaign, said many of the delegates weren't bound and could still switch their votes to Santorum.

Tuesday night's results marked the continuation of a long, hard-fought Republican nomination fight -- and underscored Romney's persistent weakness with conservatives, particularly in the GOP's regional stronghold of the Deep South.

"The fact is, in both states, the conservative candidates got nearly 70 percent of the vote," Gingrich crowed after placing second in Alabama and Mississippi. "If you're the front-runner and you keep coming in third, you're not much of a front-runner."

Romney had been hoping for at least one Southern victory Tuesday that might have allowed him to start arguing it was time for the party to gather behind him and begin the general election fight against President Barack Obama.

Instead, Romney now faces a resurgent Santorum -- and he is without the overwhelming financial advantage he boasted throughout the early states. Romney's campaign trimmed some spending in recent weeks as he was forced to spend more time campaigning and less time fundraising. Still, he's got more delegates than his rivals combined.

Santorum's victories Tuesday were worth at least 35 delegates, but Romney won at least 41. Gingrich won at least 24, while Ron Paul picked up at least one. The delegate split underscored the difficulty Romney's rivals face in overcoming his big lead.

The partial allocation of delegates from Tuesday's voting states left Romney with 495 in The Associated Press count, out of the 1,144 needed to win the nomination. Santorum had 252, Gingrich 131 and Paul 48.

And while Santorum in particular challenges the mathematical projections, Romney is amassing delegates at a rate that puts him on track to clinch control of the nomination before the convention next summer.

A senior Romney adviser, Jim Talent, said the campaign is where it needs to be. "We're really running against the delegate totals more than any of the others," Talent told CNN on Wednesday.

Gingrich deputy campaign manager Vince Haley suggested the former House speaker was putting himself in position to compete at a brokered convention, saying Gingrich could "win a debate in this country over the course of the rest of this campaign."

It is rare for Alabama and Mississippi to play an important role in a Republican nominating campaign, but the 2012 race has gone on far longer than usual.

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Associated Press writers Stephen Ohlemacher and Connie Cass in Washington contributed to this report.